The disclosure generally relates to printing processes and, more particularly, relates to lithographic printing.
Lithographic printers typically employ two liquids, i.e., an ink and a fountain solution, in conducting the printing process. The ink covers an image area of a lithographic plate to produce text and graphics on the paper being printed. The fountain solution, which is a water-based chemical solution, covers the non-image areas of the plate to keep the rest of the paper free from being printed with ink.
During the printing process, the ink is mixed with the fountain solution producing an ink/water emulsion. The balance between the two liquids needs to be accurately maintained for proper printing to occur. If the water content in the emulsion becomes too high or too low, the print quality will be degraded. Ink and water balancing in the emulsion is especially important for a keyless printing press, where unused ink is scraped off a scraping roller of an ink train and re-circulated to the ink applicator through one or more ink hoses or conduits. Since the diameter of a typical ink hose is relatively small, e.g., about eight millimeters, proper ink and water balancing is also important to, among other things, ensure proper viscosity in the emulsion and thus adequate flow through the conduit.
In accordance with one aspect of the disclosure, a water sensor for a lithographic printing press is provided which includes an enclosure having an emulsion input and an emulsion output, a chamber extending through the enclosure and fluidically connecting the input to the output, and a capacitive sensor mounted in the enclosure proximate the chamber.
In accordance with another aspect of the disclosure, a printing press is provided which includes a frame, a plurality of rollers adapted to traverse a web of paper through the frame to be printed, an ink train adapted to carry an ink/water emulsion to at least one print roller, a water content sensor in fluid communication with the ink/water emulsion, and an operator interface device in electrical communication with the water content sensor.
These and other aspects and features of the disclosure will become more apparent from the following detailed description when taken in conjunction with the accompanying drawings.